 In this video I'm going to explain a little bit for where we're getting our data from for this Hubble's law part of the lab. There's an astronomical database, and this is the website for it, and it's the NASA extragalactic database, or NED, and it's the Redshift Independent Distances. So they found distances, not using Hubble's law, but using other methods, to a wide variety of galaxies. And they've compiled that in a comma-separated value file. Now if you look at this file, it's just a big text file with lots of information in it. It's a little bit difficult to work with. So I've done a little bit of processing for you. I've read this file into an interactive programming language called Python. And after I've read it in, I've done a little bit of separating out, so I only grabbed the distances which also have red shifts, and then converted that red shift into a velocity. Now when I do that, and I make a plot of it, I can plot the distance versus the velocity for everything in that database that has both of those values. And you notice there's a lot of spread over here. We're going to focus in on the lower portion of this graph, which only goes out to 400 megaparsecs. And when we look at that part of the plot, you can already start to see part of Hubble's relationship in terms of it tends to fall along a line. Now there's still a little bit of scatter to it, and that's because real data has some errors on it. Now this set still has 6,695 data points in it, which is workable, but it's a little bit more difficult for students to download files that are that large. So I've gone through and randomly selected 200 points. Now I didn't do this individually, I had the computer do that. And so your subset that you're going to work with, the computer randomly selected 200 data points, and these are the ones that are shown here in red. I also created a second subset that I'm going to walk you through how to create the graph and find the equation.